[Bug c++/94185] New: gcc-10 crashes with "error: unable to generate reloads for {*zero_extendsidi2} internal compiler error: in curr_insn_transform, at lra-constraints.c:4006

["slyfox at inbox dot ru" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94185

            Bug ID: 94185
           Summary: gcc-10 crashes with "error: unable to generate reloads
                    for {*zero_extendsidi2} internal compiler error: in
                    curr_insn_transform, at lra-constraints.c:4006
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at inbox dot ru
  Target Milestone: ---

Created attachment 48037
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48037&action=edit
bug.cc

Originally observed on smartmontools-7.0, reduced with creduce down to:

struct a {
  int b;
  int c();
  a() : b(c()) {}
  ~a();
  char *e();
};
struct f {
  void g(int);
};
struct ar {
  int au[256];
  f h(int);
} bb;
a i();
a j(int);
long k(int, ar);
int d;
void l(char *, ar m, long n) {
  switch (m.au[d])
  case 0:
    n &= 4294967295;
  bb.h(0).g(n);
}
void o() {
  ar bd;
  a bh, bi, attrname = j(0) = i();
  int be = k(0, bd);
  l(attrname.e(), bd, be);
}

Exact command to crash gcc-master:

$ ./xg++ -B. -O2 -c -o /tmp/bug.o /tmp/bug.cc -fstack-protector-strong -fPIE
/tmp/bug.cc: In function 'void o()':
/tmp/bug.cc:30:1: error: unable to generate reloads for:
   30 | }
      | ^
(insn 62 61 63 8 (set (mem/c:DI (plus:DI (reg/f:DI 19 frame)
                (const_int -2152 [0xfffffffffffff798])) [7 %sfp+-2104 S8 A64])
        (zero_extend:DI (mem/c:SI (plus:DI (reg/f:DI 19 frame)
                    (const_int -2152 [0xfffffffffffff798])) [7 %sfp+-2104 S4
A64]))) "/tmp/bug.cc":22:7 114 {*zero_extendsidi2}
     (nil))
during RTL pass: reload
/tmp/bug.cc:30:1: internal compiler error: in curr_insn_transform, at
lra-constraints.c:4006
0x7fc532a94dd9 __libc_start_main
        ../csu/libc-start.c:308
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

Compiler is built as:

$ ./xg++ -B. -v
Reading specs from ./specs
COLLECT_GCC=./xg++
COLLECT_LTO_WRAPPER=./lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --enable-languages=c,c++ --disable-bootstrap
--with-multilib-list=m64
--prefix=/home/slyfox/dev/git/gcc-native-quick/../gcc-native-quick-installed
--disable-nls --without-isl --disable-libsanitizer --disable-libvtv
--disable-libgomp --disable-libstdcxx-pch --disable-libunwind-exceptions
CFLAGS='-O1 ' CXXFLAGS='-O1 ' --with-sysroot=/usr/x86_64-HEAD-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.0.1 20200315 (experimental) (GCC)